The present disclosure relates to apparatuses or devices that can be used to determine whether a patient has strabismus and/or quantify the angle of strabismus for surgery or other corrective method that uses the angle of strabismus. Methods of using the apparatuses and methods of determining the angle of strabismus using data obtained from the apparatuses are also described herein.
Strabismus (commonly called “cross eyes” or “wall-eyed” or “squint”) is a condition in which the eyes do not align in the same direction when focusing. Six different extraocular muscles surround the eyes and work together to focus both eyes on the same object. In a patient with strabismus, the muscles do not work together properly. When one eye focuses on a given object, the other eye is out of focus on the given object. When this occurs, two different images are sent to the brain, one from each eye (one in focus and one out of focus. This misalignment of the eyes prevents proper binocular vision and can reduce depth perception. In addition, because the brain cannot reconcile the mismatched images, the brain may learn to ignore the signal from the weaker eye, causing this eye to go blind.
Early diagnosis and correction or strabismus is the key to preventing blindness. Thus, strabismus should be detected in the first three years of a child's life. Unfortunately, while it is possible to diagnose strabismus in cooperative patients, diagnosing strabismus in non-cooperative patients is subjective and even experienced clinicians face inconsistent measurements. Up to 4% of children in the United States are affected by strabismus. The screening examinations used to diagnose strabismus are difficult with young children and infants, who are more likely to be non-cooperative due to difficulties in communication and comprehension.
The current standard in the diagnosis and treatment of strabismus of communicative adults is to perform the prism and alternate cover test (PACT). This method is effective, but requires the person performing the test to be a well trained and experienced examiner in order to be accurate. If the patient is a young child or uncommunicative, the standard is the Hirschberg test. In the Hirschberg test, the angle of deviation of the corneal light reflex within the pupil is determined.
One common treatment for strabismus is surgery to correct the muscles that control the movement of the eyes. Accurate diagnosis and measurement of the degree of deviation, i.e. the angle of strabismus, is helpful to ensure the success of the surgery and prevent the need for multiple procedures.
It would be desirable to provide apparatuses and/or methods that can permit strabismus to be determined for noncooperative patients and by lesser trained persons.